Buying my first Dive Computer need a little help

[Diving Dubai]

Different computers don't change the amount of nitrogen you are being saturated with, they are offering different levels of "protection" to try to ensure that statically you can off gas safely with no ill effects. If you draw a line with getting a DCS on one side of it and being okay on the other, then how close you sail to that line is up to you. The simple fact is that we don't actually know where that line is, and the position changes not only between people but how a person is on that day.

I'm not trying to say people must dive a conservative computer, my point is that conservatism is more than just how many minutes at different depths.

Regarding the tables kindly posted by @scubadada, while I'm not going to criticise the way they do it because smarter people than I devised the test. It's a comparison rather than real world.

If I look at dive 1 parameters (time and depth) ignoring the 60min @15' (which I assume is to de-sat the computers) My very rough calcs scribbled on a bit of paper would suggest that a person would need a HP130 with a starting pressure of 3300psi and a SAC of 0.35 for them to surface near to 500psi (I worked it out in metric and used a converter so forgive me for inaccuracies. It's not exact but demonstrate what I mean. Even my calcs don't resemble real life as they don't allow for filling the BCD etc. My point is only a minority of single tank divers will manage this dive in theroy.

In practice a 1hr 46min dive, which is well off what the majority of divers would do regularly.


Lets play a game...

Using EANx 32% and a square profile dive to 100' what is considered an acceptable NDL by you personally

 

[scubadada]

Different computers don't change the amount of nitrogen you are being saturated with, they are offering different levels of "protection" to try to ensure that statically you can off gas safely with no ill effects. If you draw a line with getting a DCS on one side of it and being okay on the other, then how close you sail to that line is up to you. The simple fact is that we don't actually know where that line is, and the position changes not only between people but how a person is on that day.

I'm not trying to say people must dive a conservative computer, my point is that conservatism is more than just how many minutes at different depths.

Regarding the tables kindly posted by @scubadada, while I'm not going to criticise the way they do it because smarter people than I devised the test. It's a comparison rather than real world.

If I look at dive 1 parameters (time and depth) ignoring the 60min @15' (which I assume is to de-sat the computers) My very rough calcs scribbled on a bit of paper would suggest that a person would need a HP130 with a starting pressure of 3300psi and a SAC of 0.35 for them to surface near to 500psi (I worked it out in metric and used a converter so forgive me for inaccuracies. It's not exact but demonstrate what I mean. Even my calcs don't resemble real life as they don't allow for filling the BCD etc. My point is only a minority of single tank divers will manage this dive in theroy.

In practice a 1hr 46min dive, which is well off what the majority of divers would do regularly.


Lets play a game...

Using EANx 32% and a square profile dive to 100' what is considered an acceptable NDL by you personally

Hi Diving Dubai,

You misinterpreted the dive tables, those are cumulative dive times, not the time at each depth. The average depth for each dive is also given beside the graphic for each dive, from which you can directly calculate gas consumption. These are all reasonable rec dives without deco. Even the most conservative computers were able to run these profiles

I run DSAT and have 30 minutes at 100 feet on EAN32

Good diving, Craig

 

[Ojai Diver]

I have yet to come across any computer that will provide additional relevant info that I would need for recreational diving over my Aladin Pro Nitrox(1997). BTW, I have to shine my torch to read the screen during night dive.

I hear many divers with new computers who complain about their unreliability, small screens, or complexity. How sad. I like my circa 1992 Swiss Made U.S.. Divers Monitor 1. Simple, easy to read, safe, and never does odd/strange behavior. No gimmicks.

 

[scubadada]

I hear many divers with new computers who complain about their unreliability, small screens, or complexity. How sad. I like my circa 1992 Swiss Made U.S.. Divers Monitor 1. Simple, easy to read, safe, and never does odd/strange behavior. No gimmicks.

And no nitrox?

 

[Ojai Diver]

Nope.

 

[Centrals]

And no nitrox?

My first computer Uwatec Aladin Pro)1996) was Nitrox compatible to 21% ONLY. Unfortunately it passed away couple of yrs ago.

 

[Diving Dubai]

I run DSAT and have 30 minutes at 100 feet on EAN32

Good diving, Craig

Hi Craig,

Thanks for the clarification. My mistake (with my mitigating factors of) perhaps not enough coffee, and rushing to pack for diving

Good info on your DSAT. I run sRGBM on the Eon and I get roughly the same (30 mins at 100') I wonder what others get?

 

[RainPilot]

I am. Looking for those same 2 things in a dive computer. I know the suunto d4i novo has a wireless transmission but I am not exactly sure if it comes with a digital compass. But it's watch-sized... Some people say it's harder to read. I'm also watch shopping and have been looking g at this one.

I was also looking at the Oceanic Veo 2.0 and you can program 2 gases with it.. For example of you do a deep dive and you don't have enough air for your safety stop you can use the pony bottle hanging down from the surface and make that your second tank... That's a little too advance for me to as I'm still open water.

Hi Nikole

The D4i does not have a digital compass.

The multi gases setting on a dive computer is for when you change type of gas during a dive, not the tank. That being said, it is possible that you may be diving Nitrox and the boat puts down a drop tank of air for people in an emergency. Thats pretty unlikely to affect you at the safety stop though, as you are doing a no-deco dive so you could finish your safety stop on the drop tank, or not, no harm no foul.

A VERY important point, even if there is a drop tank etc etc we should NEVER consider running out of air to be a normal thing, Im sure you know this but it bears repeating for the people who tend to come onto "first computer" threads. If you want to know a bit more about gas planning for basic open water dives, drop me a PM and Ill be happy to help you out.

You're welcome @scubadada

 

[stuartv]

The multi gases setting on a dive computer is for when you change type of gas during a dive, not the tank.

The most often-cited reason that I've seen for people wanting multi-gas support on a recreational computer is actually precisely for changing the computer when they change tanks.

It's hard for me to even imagine a recreational diver getting low or running out of air, switching to a hang bottle, and also doing a gas switch on their computer.

Some people seem to think that having, say, 3 gas support, setting one to air, one to EAN32, and one to EAN36, makes it easier to manage their computer when they change cylinders than just changing the actual FO2 setting when necessary.

Personally, I think multi-gas support on a recreational computer is pure marketing bunk. My rec computer supports 3 gases and I have never used anything but gas 1, on a recreational dive. Changing the FO2 is just as easy as changing the gas. And, side note, multi-gas is especially useless on a recreational computer that is using AI. Unless you are going to have an additional transmitter for each gas setting...

 

[Diving Dubai]

@stuartv

I can't disagree with you, although the divide between rec and tech is becoming a bit blurred. You might find it interesting that BSAC on their Ocean Diver (equivalent to OW + AOW) teach tables that include Decompression areas for calculations, and then Sports Diver (think of it a Advanced AOW & Rescue) teach Planned decompression on a single gas. You can then get an additional qual of Accelerated Decompression (which I surmise but don't know would be similar to AN/DP) so as a rec diver under BSAC you do get involved with Mixed gas.

When I completed my BSAC Dive Leader (DM equivalent) I had to suddenly learn BSAC tables, which I assumed wouldn't be difficult right? How wrong was I? The even have calculations which take into account the Air Pressure at Sea Level and take into account the height of the hill you may have driven over to get to the dive site. I had to take a whole day of theroy on BSAC Air and Nitrox tables to get me up to speed